1. Field of the Invention
The present invention relates to novel acrylate or methacrylate derivatives and photoresists containing the polymers thereof. More particularly, the present invention relates to organometal-containing acrylate or methacrylate derivatives and photoresists which make it possible to use a microlithographic process comprising a dry development step which can advantageously prevent the deformation or collapse of patterns, which is aggravated as their aspect ratio increases.
2. Description of the Prior Art
The high integration of semiconductor devices has always been supported by a significant advance in microlithography, a core technique in the art and thus, followed by a momentous progress in photoresist. One of the most widely used photoresists is that which comprises a styrenic polymer which is usually synthesized by free radical, cationic or anionic polymerization and which is changeable in chemical properties when being exposed to deep UV light.
A detailed description is disclosed in U.S. Pat. No. 4,491,628 of a resist which comprises a polymer with an acid labile side chain, such as t-butyl ester or t-butyl carbonate, and a photoacid generator which produces acid upon exposure to UV light. The selected polymer is a vinyl polymer, such as polystyrene or polyacrylate while the photoacid generator is an onium salt, such as diaryliodonium salt or triarylsulfonium salt. At the regions irradiated with UV light, acid is generated, detaching the acid labile protecting groups from the main chain, which makes the polymer have a different polarity from that of non-irradiated regions. Taking advantage of this difference in polarity, a polar or non-polar developing solution enables the photoresist to express a negative or positive image.
When being applied for microelectronics, such a solution-developable photoresist has a serious problem: the patterns are more easily deformed and collapsed upon wet developing and rinsing as their aspect ratio (ratio of height to width) increases. In order to avoid this problem, several measures were taken, including use of a matrix polymer of high strength or high adhesiveness to the substrate and selection of proper developing solution and rinsing solvent.
However, because the increase of the aspect ratio is indispensable while the adhesiveness cannot exceed a limit, the measures have to be used restrictively. For these reasons, there is a need for developing a novel resist which is dry-developable by using, for example, anisotropic O.sub.2 reactive ion etching (RIE).